This week on Under the Covers, Gill speaks with David Glynn about the secret lives of the authors we love.

His book Five Billion Sold: The Amazing Facts Behind the Fiction explores the lives of 30 authors, each of whom has sold at least 50 million copies of their books, including JK Rowling, Agatha Christie, JRR Tolkien, Wilbur Smith, Danielle Steel, John Grisham and Colleen McCullough among others.